Steel converter vessel pollution control method and apparatus

ABSTRACT

The hot evolved gases from a bottom blown steel converter vessel are delivered to a spray chamber near the vessel in which the gases are cooled by sufficient amount to make them acceptable to a remotely situated electrostatic precipitator in which finely divided solids are removed from the gases. The clean gas is withdrawn from the precipitator with a suction fan and delivered to a stack which discharges the gases to the atmosphere.

0 llmted States Patent 1 [111 3,

Dortenzo Jan. 29, 1974 [54] STEEL CONVERTER VESSEL POLLUTION 3,026,1023/ 1962 McFeaters 266/35 CQ METHOD AND APPARATUS 3,236,630 2/ 1966Stephan 75/60 3,314,781 4/1967 Johannsson et a1 75/60 [75] n o Alexandero ten Plttsburgh, 3,330,645 7/1967 Moustier et a1 75/60 Pa. 3,599,9498/1971 Grenfell 75/60 ss gnee: Pennsylvania Engineering 3,603,572 9/1971Rosentem 266/35 Corporation Pittsburgh Primary Examiner-Gerald A. Dost[22] Filed: Feb. 23, 1972 Attorney, Agent, or FirmRa1ph G. Hohenfeldt eta1.

[21] Appl. No.: 228,528

[57] ABSTRACT 52 US. Cl 266/13 266/15 266/35 T hot evolved gases a blowSteel [51 Int. Cl. C2lc 5/48 verter vessel are delivered to a SprayChamber near the [58] Field of Search. 266/35 13 36 P 15 I6 vessel inwhich the gases are cooled by sufficient 75/5l 4 6 amount to make themacceptable to a remotely situated electrostatic precipitator in whichfinely divided [56] References Cited solids are removed from the gases.The clean gas is withdrawn from the precipitator with a suction fanUNITED STATES PATENTS and delivered to a stack which discharges thegases to 741,505 10/1903 'Kirk 266/36 P the atmosphere 1,505,281 8/1924Nagelvoort 2,803,450 8/1957 McFeaters 266/35 2 Claims, 2 Drawing FiguresPATENTEU 3.788.619

SHEU 1 OF 2 FIG.]

STEEL CONVERTER VESSEL POLLUTION CONTROL METHOD AND APPARATUS BACKGROUNDOF THE INVENTION The present invention is particularly advantageous inconnection with modifying existing open hearth steel making plants foruse of bottom blown converter vessels although the invention may be usedin new plants too.

' It is well known that in the open hearth process which is stillextensively used in the United States for making steel it is difficultto prevent gas and smoke that is incidental to the process from escapinginto the atmosphere and polluting it. On the other hand, it has beenrecognized that air pollution can be abated significantly by use ofbasic oxygen converter vessels in place of open hearth converters.Adapting open hearth plants for top blown basic oxygen converter vesselshas, however, been deterred because of the large expense of modifyingexisting buildings to accommodate the taller converter vessels and theirassociated equipment. Much greater head room or roof height is requiredfor top blown basic oxygen converter vessels because they use an oxygenlance which must be inserted through the top mouth of the vessel. Oxygenlances are usually more than 50 feet long and are inserted in theconverter vessel in a substantially upright attitude, thus accountingfor the greater roof height that is required.

It has also been recognized that air pollution might be minimized byusing a bottom blown converter vessel instead of a top blown vessel,especially in those cases where remodeling of an open hearth plant isnecessary to meet pollution control regulations. In bottom blown steelconverter vessels, no lance is required since all gases and finelydivided fiuxing materials are introduced through tuyeres in the bottomof the vessel. The gas collection hood may be coupled closely with thevessel and a negative pressure may be maintained in the gas collectionsystem so that little of the gas evolved from the vessel during refiningescapes to the atmosphere.

In many existing open hearth plants electrostatic precipitators are usedto clean the gases of particulate solids before the gases are dischargedto the atmosphere. This is permissible in open hearth plants because thegases which are fed to the precipitator are usually below 550 P which isnot too hot for the precipitator. One of the reasons for not takingadvantage of the cleanliness capabilities of bottom blown vessels inopen hearth plant remodeling projects is that the gases which evolvefrom the vessel are extremely hot, often in the range of 3,000 to 3,500F which is too hot to be fed into an electrostatic precipitator. In somecases, therefore, otherwise operative and useful and costlyprecipitators have been discarded and expensive gas cleaning systemsusing venturi scrubbers are specified. This sometimes increases theprospective cost of remodeling an existing open hearth plant to suchextent taking the plant out of service might be dictated in preferenceto trying to meet pollution abatement requirements.

SUMMARY OF THE INVENTION In accordance with the invention, the highlyeffective gas cleaning characteristics of electrostatic precipitatorscan be utilized in either new plants or remodeled existing open hearthplants by using bottom blown converter vessels in association with a gashandling system that enables delivering dirty gas from the convertervessel to the precipitator at temperatures which are tolerable to thelatter.

Objects of the present invention are to provide a gas cleaning systemwhich requires little space and can be easily fit into a new plantwithout sacrifice of otherwise usable space and which may readily be fitinto an existing plant in such manner that existing gas handlingequipment requires minimum modification.

Another object is to situate inexpensive gas cooling equipment inproximity with a bottom blown converter vessel in such manner that mostof the piping system and the precipitator are required to handle gasesat relatively low temperatures.

A more general object is to improve the economics of complying withpollution abatement requirements in connection with remodeling existingsteel converter plants and new plants.

How the foregoing and other more specific objects are achieved willappear throughout the course of a detailed description of an embodimentof the invention which will be set forth shortly hereinafter.

In general terms, the invention is characterized as an arrangementwherein there are one or more bottom blown steel converter vessels in abuilding. Each vessel has a water-cooled hood removably located over itsmouth and a water-cooled duct connects to the hood. As near as possibleto the vessel, and in a position where no interference is presented tothe cranes and other apparatus for charging the vessel and handling itsopen contents, a water spray chamber is installed. The water-cooled ductfrom the hood has a short run to the spray chamber in which the gasesevolved from the ves sel are cooled from over 3,000 to 550 F or 500 F.The relatively cool gases from each spray chamber associated with aconverter vessel are delivered to an existing or new dirty gas main towhich the inlet of an existing or new electrostatic precipitator isconnected. The latter separates particulate matter such as smoke fromthe gases which are delivered by means of an exhaust fan to a stack.Carbon monoxide is precluded from igniting in the precipitator byburning it previously in the hood or above the melt surface in thevessel.

A more detailed description of an illustrative embodiment of theinvention will now be set forth in reference to the drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic longitudinalelevation view of a steel conversion plant using bottom blown vesselsand the new gas handling system; and

FIG. 2 is a diagrammatic plan view of the equipment shown in FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIGS. l and 2 a bottom blownsteel converter vessel is generally designated by the numeral 10. Insome plants a number of such vessels are arranged in a rowlongitudinally of a building interior. Vessel 10 comprises a metal shellll which has an interior lining of refractory material l2. The vesselhas a mouth l3 at its top and a set of tuyeres 15 at its bottom. Thetuyeres extend through refractory lining 11 and are adapted to injectoxygen and other gases and fine materials entrained in gases into moltenmetal which may occupy the interior of vessel 10 to a depthapproximating the broken irregular line 16. The bottom of vessell isequipped with a chamber 17 in which there are suitable headers, notshown, which connect with tuyeres l5. Feed pipes 18 and 19 connect withthe tuyeres. Pipe 19, for instance, delivers pressurized oxygen to thetuyeres so that the oxygen may permeate the molten metal in the vesseland reduce carbon and other elements therein. Fluxes and other materialsneeded for converting molten pig iron to steel within the vessel arefinely divided and entrained in the oxygen for delivery through thetuyeres. Pipe 18 is for delivery of a hydrocarbon gas such as propanethrough suitable passageways in the tuyeres adjacent the passagewaysthrough which oxygen is injected into the molten metal. Cracking of thehydrocarbon is an endothermic reaction which cools the superheated metalin the exit region of the tuyeres which results from the oxygen-carbonreaction. Reduction of the metal temperature in this region inhibitsdeterioration of the refractory bottom of vessel which would ordinarilyresult if there were no cooling means.

Vessel 10 is supported conventionally on a trunnion ring 20 from which apair of trunnion pins 21 and 22 project. Trunnion pin 21 is journaled ina bearing structure 23 which is supported on a footing 24. Trunnion pin22 is also journaled in a bearing structure 25 which is supported on afooting 26. The mechanism for tilting vessel 10 about the axis of thetrunnion pins 21, 22 is omitted from the drawing because it is known.Trunnion pin 22 has one or more axial passageways which communicate withhydrocarbon gas pipe 18 and oxygen pipe 19 through suitable passagewaysin the trunnion ring 20. Trunnion pin 22 is connected with a swiveljoint assembly 26 which has one inlet 27 for oxygen in which finelydivided materials are entrained and another inlet 28 for hydrocarbongas. lnlets 27 and 28 remain stationarywhile other parts of the rotaryjoint assembly 26 turn along with trunnion pin 22 when the vessel istilted.

During the refining process when oxygen is being blown through moltenmetal 16 carbon dioxide, carbon monoxide, other gases, smoke and otherparticulate materials evolve from the vessel and must be prevented frompolluting the atmosphere. At the mouth 13 of the vessel,.the gases areabout 3,000 to 3,500 F, temperatures which are much too high for thegases to be delivered directly to an electrostatic precipitator forremoving the particulate matter therefrom. Accordingly, a water-cooledgas collection hood 35 is positioned over vessel 10. Hood 35 is mountedon a wheeled carriage 36 so that it may be moved away from vessel 10 ona track 37 when desired. The hood 35 is connected to a jacketedwater-cooled elbow 38 which makes a connection at 39 with a water-cooledduct 40. Although the structural details are not shown, the conicallyshaped hood 35 may be adapted for being raised and lowered with respectto vessel 10 so that the vessel may be tilted to discharge its moltencontents through a pouring spout 41 or so the vessel may be inverted todischarge slag through its mouth 13. Ladles for receiving refined moltenmetal or slag may be positioned in a pit 42 beneath vessel 10. The cartsfor supporting and moving the slag and metal ladles in pit 42 are notshown since they are conventional.

ln accordance with the invention, the hot dirty gases incidental toconverting impure ferrous metal to steel are conducted through the shortwater-cooled duct 40 to a spray chamber which is generally designated bythe reference numeral 45. lntemally of the spray chamber and near itstop there are a plurality of atomizing nozzles 46 which project finelydivided water or mist 47 vertically through spray chamber 45. Theintimate contact between the water and the evolved gases in the chamber45 results in cooling of the gases to a temperature of under 600 F andpreferably 550 F or less. At the same time some of the particulatematter in the gas settles in the bottom of the spray chamber and must beremoved periodically as sludge. Much of the fine particulate matter,however, is conveyed in the cooled gas and leaves the outlet of chamber45 through an exit pipe 48.

As can be seen in FIG. 2, spray chamber 45 is in alignmentlongitudinally of the building with vessel 10 so that the spray chamberis not in the way of the overhead crane or any other apparatus that runsalong the sides of the converter vessel for charging it with hot metal,scrap or additives or for removing the slag and molten metal ladles.More than one associated pairs of converter vessels 10 and spraychambers 45 may be arranged in a row in the interior of a single plant.Spray chambers 45 are near their associated converter vessels 10 so thatwater-cooled ducts such as of minimal length can be used for conveyingthe extremely hot gases from the vessel. in other gas cooling systems,it is not uncommon to have rather long water-cooled ducts which isdisadvantageous because such high temperature ducts are expensive tobuild and maintain. Moreover, there is a considerable cost reductioneffected in a system such as the present one where most of the gases areconveyed in a rather cool state whereupon ordinary uncooled andunjacketed piping may be used.

As can be seen in thp drawings, the gas exit pipe 48 from spray chamberconnects with a Tee 49 in an exhaust pipe 50 which runs longitudinallyof the plant and connects by means ofa riser pipe 51 to a transverseoverhead pipe 52. The overhead pipe has a branch 53 connected with theinlet 54 of an electrostatic precipitator 55. The gases which enterprecipitator 55, in accordance with the invention, are under 550 F so asto not exceed the temperature rating of the precipitator. As is known,the electrostatic precipitator removes particulate matter from the gasand the latter is drawn from the precipitator through a pipe 56 which isconnected to a motor driven exhaust fan 57 that need be the only exhaustfan used for the entire gas handling system. Even though the gas mixtureevolved from vessel 10 occupies a large volume because of itstemperature, a relatively small exhaust fan 57 may be used because gasvolume is markedly reduced by virtue of the gases being cooled as muchas 3,000 F in spray chamber 45.

The exhaust gases which are drawn out of the system by fan 57 comprisemainly carbon dioxide which is a non-pollutant. The gases are deliveredthrough a pipe 58 to the bottom chamber 59 of a stack 60 and dischargedto the atmosphere from the upper end 61. By not closing hood 35 tightlyon vessel 10 air can enter to burn evolved carbon monoxide in the hoodso that this gas cannot ignite elsewhere in the system nor can thistoxic gas be discharged to the atmosphere from the stack.

In summary, a gas cleaning arrangement for bottom blown convertervessels has been described. The system is distinguished by itsadaptability for use in new plants or in open hearth steel making plantswhich are being remodeled for use of bottom blown converter vessels. Thesystem permits use of new or existing electrostatic precipitators byvirtue of the gases evolved from the converter vessel being cooled inproximity with them and delivered to the precipitator in a lowtemperature state. The system is compact and may be installed withoutsignificant building modifications in most cases.

Thp described embodiment is intended to be illustrative rather thanlimiting for the invention may be variously embodied and is to belimited only by interpretation of the claims which follow.

I claim:

1. A steel making system characterized by its low atmospheric pollutioncharacteristics, comprising:

a. a refractory lined converter vessel having tuyere means for injectinggas and finely divided solids en trained in a gas beneath the surface ofmolten metal contained in the vessel to effectuate refinement of themetal, said converter vessel having a mouth which is at the top of thevessel during refining operations and trunnion means supporting it forrotation, said tuyere means being remote from the vessel mouth,

b. spray chamber means located adjacent one side of said vessel in suchposition that a projection of the trunnion axis would intersect saidchamber means whereby to maintain a substantially constant distancebetween said vessel and said chamber for any rotational position of saidvessel, said chamber means having an inlet and an outlet and means forspraying water into a gas stream flowing between said inlet and outletinteriorly of the chamber means to thereby cool a gas stream,

c. water-cooled hood means positionable above the mouth of said vesselto collect gas evolved therefrom which gas contains particulatesubstances and is relatively hot,

d. water-cooled duct means interconnecting said hood means with theinlet of said chamber means,

e. electrostatic precipitator means located at a side of said vesselopposite from the side on which said spray chamber is located and at anelevation substantially above the elevation of the bottom of saidvessel, said precipitator means having an inlet and an outlet,

f. pipe means having a part connected to the outlet of said spraychamber means at one elevation and another part extending in parallelismwith the axis of said trunnion means at the same one elevation and stillanother part rising to a higher elevation and connected with the inletof said precipitator means,

g. exhaust fan means having an inlet coupled to the outlet of saidprecipitator means and having an outlet, said fan means being operativeto draw gas through the entire system including the hood means, ductmeans, spray chamber means, pipe means and precipitator means.

2. The system defined in claim 1 including:

a. a stack means having an inlet coupled with the outlet of said fanmeans.

1. A steel making system characterized by its low atmospheric pollutioncharacteristics, comprising: a. a refractory lined converter vesselhaving tuyere means for injecting gas and finely divided solidsentrained in a gas beneath the surface of molten metal contained in thevessel to effectuate refinement of the metal, said converter vesselhaving a mouth which is at the top of the vessel during refiningoperations and trunnion means supporting it for rotation, said tuyeremeans being remoTe from the vessel mouth, b. spray chamber means locatedadjacent one side of said vessel in such position that a projection ofthe trunnion axis would intersect said chamber means whereby to maintaina substantially constant distance between said vessel and said chamberfor any rotational position of said vessel, said chamber means having aninlet and an outlet and means for spraying water into a gas streamflowing between said inlet and outlet interiorly of the chamber means tothereby cool a gas stream, c. water-cooled hood means positionable abovethe mouth of said vessel to collect gas evolved therefrom which gascontains particulate substances and is relatively hot, d. water-cooledduct means interconnecting said hood means with the inlet of saidchamber means, e. electrostatic precipitator means located at a side ofsaid vessel opposite from the side on which said spray chamber islocated and at an elevation substantially above the elevation of thebottom of said vessel, said precipitator means having an inlet and anoutlet, f. pipe means having a part connected to the outlet of saidspray chamber means at one elevation and another part extending inparallelism with the axis of said trunnion means at the same oneelevation and still another part rising to a higher elevation andconnected with the inlet of said precipitator means, g. exhaust fanmeans having an inlet coupled to the outlet of said precipitator meansand having an outlet, said fan means being operative to draw gas throughthe entire system including the hood means, duct means, spray chambermeans, pipe means and precipitator means.
 2. The system defined in claim1 including: a. a stack means having an inlet coupled with the outlet ofsaid fan means.